Many portable electronic systems, such as laptop computers and cellular phones, are powered by rechargeable batteries. Such batteries have the advantage that they are portable, relatively weight efficient, and can be charged and discharged many times. However, the high performance of these electronic systems require efficient utilization of the rechargeable battery. But due to certain characteristics of rechargeable batteries, the efficient and optimal control of rechargeable batteries is very difficult.
For example, a rechargeable battery that is fully charged needs to be maintained at maximum readiness by applying a very small current to the rechargeable battery. Further, with many rechargeable batteries, such as Ni--Cd batteries, the voltage of the rechargeable battery will drop at full charge. Therefore, it is very important to be able to communicate to a recharger system when the rechargeable battery is fully charged and has reached its optimal potential.
In addition, the operation of rechargeable batteries will be affected by operating temperature of the system utilizing the rechargeable battery. For example, a rate of discharge which is not excessive at one temperature may be excessive at another temperature.
As can be appreciated, the optimal management of the rechargeable battery whether during charging or discharging is very critical. For example, it is very desirable to monitor the potential level of a rechargeable battery in a laptop, so that if the potential level of the rechargeable battery falls below a certain threshold, the computer can be safely shut down before the computer crashes, potentially losing information. Therefore, the more information the electronic systems interfacing with the rechargeable battery have, the more efficiently the rechargeable battery as well as the electronic system itself can be utilized.